The publications and other materials used herein to illuminate the background of the invention, and in particular, the cases to provide additional details respecting the practice, are incorporated by reference.
The delivery system discussed in this application mainly covers intrauterine systems (IUS), intracervical systems and intravaginal systems. The systems usually consist of a body and a capsule containing one or more pharmaceutically active agents. A commonly used intrauterine system is a T-shaped object fabricated of plastic material, which object consists of an elongate member having at one end a transverse member comprising two wings, the elongate member and the transverse member forming a substantially T-shaped piece when the system is positioned in the uterus. The elongate member has for example a copper wire wound partly around it, said wire being capable of releasing copper ions (and corresponding to the above-mentioned capsule containing the pharmaceutically active agent). Also IUS's capable of releasing hormones or other active agents exist, and they are used either for contraception or for the treatment of hormonal disorders. In addition to T-shaped IUS's also systems shaped like a ring, a “7” or an “S”, for example, are known. Similar constructions are used for the intracervical and intravaginal systems.
The manufacturing process of these systems commonly consists of separate manufacturing of the body and the capsule followed by their assembly. Said assembly is usually performed simply by pulling the capsule over the body, for example over one of the wings. At the beginning of the use of the system, the capsule is tight on the body. However, at the end of the period of use, typically when the capsule has released 30-60% of its content in the active agent, it loosens up and may detach from the body either during the use or at the moment of removal of the system from the body cavity.
The systems are introduced to the appropriate body cavity usually by means of an inserter. Several types of inserters exist for the positioning of intrauterine systems. The most common inserter for T-shaped IUS's consists of a protective tube having a plunger with a handle inside it. In preparation for the positioning of the system in the uterus, the IUS, which is located at the end of the plunger, is retracted towards the handle so that the system enters the tube, and the wings of the transverse member of the system bend towards each other. Then the protecting tube with its contained IUS is introduced through the cervical canal. When the system is correctly positioned it is released by retracting the protecting tube towards the outside. The wings of the transverse member then expand, and the system assumes the shape of a “T”.
A problem is associated with the inserters of T-shaped systems and other systems as described above regarding the positioning of the capsule over the body during the retraction of the protective tube towards the outside. The inner diameter of the inserter should be sufficiently larger than the outer diameter of the system to be inserted in order to avoid the shifting or complete detachment of the capsule. However, one has to take into account that the hemispherical end pieces of the wings of the transverse member are small in relation to the diameter of the protective tube. It is, therefore, extremely important that these end pieces are in the exactly correct position in relation to the edge of the protective tube at the moment of introducing the system in the uterus, and therefore the inner diameter of the protective tube cannot be considerably larger than the outer diameter of the system. The difference of the diameters is typically 0.05-0.1 mm. The system is usually sold positioned in the inserter but in the case that the physician unintentionally releases the system too early, it may be very difficult to reposition it correctly in the inserter.
The incorrect positioning of the system in the inserter may cause various problems, such as the shifting of the capsule on the body, the deformation of the capsule, the deterioration of the capsule or the detachment of the capsule.
The shifting of the capsule can for example occur in such a manner that the capsule is displaced towards the wing of the T-shaped system, thus changing the shape to Y and hindering the correct positioning of the wings thus preventing the use of the system. The deterioration or deformation of the capsule may alter the release of the active agent from the capsule.
As discussed above, essentially two problems may occur during the manufacturing of the systems, their introduction into the appropriate body cavity of a patient and their use. These problems are how to assemble the body and the capsule and how to maintain the body and the capsule together during the introduction and the period of use of the system, which may be several years, typically up to five years.
Some solutions to these problems are given in the prior art. For example, the U.S. Pat. No. 4,341,728 discloses a method of making an IUS with shrinking of a medicated attachment onto a support. In said method, a mixture of silicone and a drug is injection moulded to form a sleeve, which is then swollen by immersion in a solvent and subsequently slipped onto a stem of the IUS to shrink about the stem. An outer covering may be positioned over the sleeve in a similar manner. The disadvantage of this method is the use of a solvent. Residues of solvent may remain in the sleeves and cause irritation once the IUS is placed in the patient's uterus. Furthermore, part of the drug may dissolve into the solvent used, thus causing the amount of drug in the final IUS being less than expected. This method does also not solve the problem of maintaining the capsule on the body over the whole period of use of the system.
The U.S. Pat. No. 3,973,560 discloses an IUS consisting of a body and a copper wire, wherein the surface of said body comprises serrations that act as guides for the copper wire and maintain it in place. The disadvantage of this structure is, however, that it is not useful for delivery systems releasing hormones, since these systems do not comprise a wire but rather a tube consisting essentially of an elastomer comprising one or more active agents.
The U.S. Pat. No. 3,656,483 discloses an IUS that consists of a perforated tube containing a supply of medications. The medication is maintained adjacent the perforations by a spring arrangement.